Growth of Hg‐based alloys by the traveling heater method

Abstract

Oriented (Hg,Cd)Te single crystals have been grown by the traveling heater method. The crystals were grown in the 〈111〉A and 〈111〉B directions. Growth along the 〈111〉B direction yields single crystals whereas those grown in the 〈111〉A direction show a high density of microtwins. The crystalline quality as determined by chemical etching and x‐ray rocking curves indicates that the crystals have a low‐line defect density. The dislocation density is found to be in the 3×104 cm−2 to 2×105 cm−2 range and the subgrain boundary density is lower for crystals grown in the 〈111〉B direction. Thermal analysis was carried out using a finite element model. The analysis shows that a convex interface can be achieved under the appropriate thermal conditions and the simulations are found to be in good agreement with the experimental data. The macrostructure of the crystals clearly indicate that when the interface is convex a single crystal is obtained but when the interface becomes concave, crystals are nucleated at the ampoule wall. The crystals were evaluated by Hall‐effect measurements and metal–insulator–semiconductor (MIS) device performance. The carrier concentration at 77 K ranges from 1×1014 to 5×1014 cm−3 for crystals with a [CdTe]=0.22–0.24 and the mobility ranges from 1.8×105 to 1×105 cm2/V s. The dark currents as measured from MIS devices for crystals having spectral cutoff wavelengths in the range of 10 to 10.5 μm range from 1×10−4 to 2×10−4 A cm−2. These values are within a factor of 10 of those estimated from the Auger limit.